Question

Decomposition temperature of $CaC{O}_3$ (s) is approximately $900{}^{0}C$. Which of the following decompose below $900{}^{0}C$?

• A. $BeC{O}_3,MgC{O}_3$
• B. $SrC{O}_3,BaC{O}_3$
• C. $BeC{O}_3,BaC{O}_3$
• D. $MgC{O}_3,SrC{O}_3$

Answer 1

The correct option is A $BeC{O}_3,MgC{O}_3$

The thermal stability of alkaline earth metal carbonates decreases with decrease in size of the cation due to the polarization of larger carbonate anion by the cation. The less stable carbonates decomposes at lower temperatures than more stable carbonates. Hence, $BeC{O}_3$ and $MgC{O}_3$ which has smaller cations than $CaC{O}_3$ has decompostion temperatures lower than ${900}^{\circ }C$